package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    private  final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id , Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        String key=keyPrefix+id;
        //从redis中查缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //判断是否存在
        if (StrUtil.isNotBlank(json)){
            //存在，直接返回

            return JSONUtil.toBean(json,type);
        }
        //判断命中是否是空值
        if (json != null){
            return null;
        }
            R r=dbFallback.apply(id);
            //不存在，返回错误
            if (r == null){
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            //存在，写入缓存,设置有效时间
            this.set(key,r,time,unit);
            //释放互斥锁
        //返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public <R,ID> R queryWithLogicalExpire(String keyPrefix, ID id , Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        String key=keyPrefix+id;
        //从redis中查缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //判断是否存在
        if (StrUtil.isBlank(json)){
            //不存在，直接返回
            return null;
        }
        //命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //未过期，直接返回店铺信息
            return r;
        }
        //已过期需要缓存重建
        //缓存重建
        //获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //判断是否获取成功
        if (!isLock) {
            //成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    R r1 = dbFallback.apply(id);
                    //寫入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //失败，返回过期的商铺信息
        return r;
    }

    //尝试获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }
}
